Cylinder block of a hydraulic unit and method of making same



Oct 25, 1956 w. LEEMING ETAL 3,280,758

KING SAME 2 Sheets-Sheet l CYLINDER BLOCK OF A HYDRAULIC UNIT AND METHODOF MA Filed Sept. 24, 1964 WU" W1 0 5 T.. w l mm: 7 M 5 M HM h 2 mm 4 1w 4 m T M w M M J 1 0 mu;

INVENTORS WILSON LEEMING JAMES E. KNABE RICHAIQD C. BRITTON Wm! M '9$711 @lltP/s.

Oct. 25, 1966 w. LEEMING ETAL 3,280,758

CYLINDER BLOCK OF A HYDRAULIC UNIT AND METHOD OF MAKING SAME 1 FiledSept. 24, 1964 2 sheetvS-sheet 2 STEELv 61 BOND LINE DIFFUSION 60 ZONEBRONZE -@gg 2 BONDED 111R 20 MIN. AT I575F. 80.I0.IO BRONZE 52100 STEELg MCHROMIUM -1 OOPPER 59 INTERFACE MTIN' 0g COPPER CHROMIUM TIN\-\ I 0I.I|A|AIAI.I II I I60 I40 I I00 8 0 60 40 20 0 20 40 6O 80 I00 I20DISTANCE, MICRONS g 2 l k BONDED 3 HRS. AT I575 1-. P5 80.IO.IO BRONZE52100/5TEE1. I Z

Io MCHROMIUM INTERFACE-)1- flflflcoppER 8 CHROMIUM TIN I60 I I20 I00 8040 20 0 20 40 60 I00 I20 DISTANCE, MICRONS United States Patent3,23%,758 CYLINDER BLOCK 0F A HYDRAULIC UNIT AND METHDD (9F MAKING SAMEWilson Learning, James E. lKn'abe, and Richard C. Britton, Rockford,iil., assigncrs to Sundstrand Corporation, a corporation of IllinoisFiled Sept. 24, 1964, Ser. No. 39?,046 17 Claims. (Cl. 1t)3162) Thisinvention relates to hydraulic pump and motor units and particularly toa new and improved cylinder block for a hydraulic unit and a method ofmaking the cylinder block.

In one type of hydraulic unit, multiple pistons reciprocate in cylindersin a rotating cylinder block while fluid flows to and from the cylindersthrough ports such as arcuate ports in a stationary valve membersagainst which the cylinder block rotates. The cylinder block may be of aradial piston type, in which the cylinders and pistons radiate from theaxis of rotation of the cylinder block, or an axial piston type, inwhich the pistons and cylinders are formed in the cylinder blockparallel to the axis of rotation of the block or the cylinders may beinclined radially and axially relative to the axis. A cam memberstationary with respect to the cylinder block is conventionally employedto reciprocate the pistons and depending upon the position of the cammember and the direction of rotation of the cylinder block, the multiplepiston hydraulic unit may be employed as either a pump for deliveringhydraulic fluid under pressure or as a motor for driving a load.

In the rotating cylinder block of hydraulic units of the charactermentioned, there are generally two areas of critical bearing contactbetween the block and other portions of the hydraulic unit. One is thebearing surface between the pistons and the cylindrical bores in theblock, and the other is the bearing surface between one end of thecylinder block and the stationary valving member against which thecylinder block rotates. It is extremely desirable to construct theseareas of the cylinder block of a suitable bearing material to assureproper seating of the pistons and the valve member relative to thecylinder block. However, it is often impractical to construct thecylinder block entirely of a suitable bearing material as this reducesthe over-all strength and temperature expansion characteristics of thecylinder block.

It is in this background that applicants have provided a hydraulic unitcylinder block constructed of high strength material with sleeves in thecylinder bores constructed of a bearing material to improve the slidingcontact characteristics between the reciprocating pistons and thecylinder bores, and with a bearing plate constructed of a suitablebearing material on one end of the cylinder block adjacent and engagingthe stationary valve member to improve the sliding contactcharacteristics between the block and the stationary valve member.Because of strenuous operating conditions normally encountered in theuse of hydraulic units of the type described, it is neces sary that thesleeves and the bearing plate be secured firmly to the cylinder block toprevent loosening or deformation of the members during use. Bymetallurgically bonding the sleeves and the valve plate to the cylinderblock by a new and improved method, a durable and long-lasting cylinderblock has been provided. The metallurgical bond is provided between thebearing material of the sleeves and the bearing plate, which may bebronze, and the high strength steel of the cylinder block, which may bea low alloy or carbon tool steel, by heating the metals while inintimate contact under a relatively low pressure to a temperature justwithin the melting range of the bearing material and in theaustenitizing range of the steel cylinder block so that a portion of thebearing material adjacent the interface diffuses across in the steeladjacent the interface.

It is, therefore, a primary object of the present invention to provide amethod of joining dissimilar metals as by diffusing a portion of thelower melting range metal adjacent the interface into the higher meltingrange metal to form an intimate metallurgical bond.

Another object of the present invention is to provide a method ofjoining a bearing metal to carbon steel by heating the metals while inintimate contact under relatively low pressure into the austenitizingrange of the steel and just within the melting range of the bearingmetal for a suflicient time so that a portion of the bearing metaladjacent the metal interface diffuses into the steel. This methodproceeds without the use of a flux or a tertiary bonding metal andresults from the intimate contact of the two metal surfaces to be joinedalong with the application of heat at a temperature and time determinedby the characteristics of the metals to be joined.

A further object of the present invention is to provide a new andimproved method of bonding cylinder sleeves to a hydraulic unit cylinderblock by press fitting the sleeves constructed of a suitable bearingmaterial into the cylinder bores of a steel cylinder block and heatingthe block to a temperature and for a time sutficient for a portion ofthe sleeves adjacent the interface to expand and liquify and diffuseinto the interstices of the steel cylinder block forming an intimatemetallurgical bond.

Another object of the present invention is to provide a new and improvedmethod of joining a bearing plate to one end of a cylinder block byclamping the bearing plate constructed of a suitable bearing material toa carbon steel cylinder block and then heating the cylinder block at atemperature and for a time sufiicient for a portion of the bearing metaladjacent the interface to difiuse into the steel forming an intimatemetallurgical bond.

A more specific object of the present invention is to provide a methodof joining cylinder sleeves and a bear ing plate both constructed ofbronze to a carbon steel cylinder block by press fitting the bronzesleeves into the cylinder bores and clamping the bronze bearing plate toone end of the cylinder block and then heating the cylin der block intothe austenitizing range of the carbon steel and just within the meltingrange of the bronze so that a portion of the copper in the bronzeadjacent the interfaces crosses thereover and diffuses into the carbonsteel adjacent the interfaces forming intimate metallurgical bonds.

Another object of the present invention is to provide a new and improvedcylinder block having a bearing metal sleeve bonded within the cylinderbores to reduce the frictional contact and improve the sliding fitbetween the pistons and the cylinder block. The sleeves are bonded tothe cylinder bores without the use of a flux or a third bonding materialwith the bond consisting purely of a ditfused portion of the bearingmetal interlaced in the material of the cylinder block.

A further object of the present invention is to provide a new andimproved cylinder block for a hydraulic unit having a bearing plateadjacent one end thereof adapted to slide against a relativelystationary valving member in which the bearing plate is metallurgicallybonded to the cylinder block and a portion of the valve plate adjacentthe interface is diffused into the steel of the cylinder block.

A still more specific object of the present invention is to provide anew and improved cylinder block for a hydraulic unit with bronze sleevesbonded Within the cylinder bores of a carbon steel cylinder block and abronze hearing plate bonded to one end of the cylinder block with aportion of the bronze in the sleeves and in the plate diffused into thecarbon steel.

Other objects and advantages will become readily apparent from thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a longitudinal cross-sectional view of the cylinder block ofthe present invention with a valve plate clamp engaging both ends of theblock in carrying out the method of the present invention;

FIG. 2 is an end elevation of the cylinder block of FIG. 1 showing thevalve plate with annularly arrayed cylin der ports therein;

FIG. 3 is an opposite end elevation of the cylinder block shown in FIG.1 showing the cylinder sleeves in place in the cylinder bores;

FIG. 4 is a photomicrograph of the metallurgical bond between thecylinder sleeves, the bearing plate and the cylinder block taken alongthe interface between the two metals;

FIG. 5 is a graph showing the diffusion of the metals adjacent theinterface in the present invention employing exemplary metals;

FIG. 6 is a graph similar to FIG. 5 showing the diffusion of the metalsadjacent the interface in the present metallurgical bond resulting froma longer bonding time than was employed in the bond exemplified by thegraph of FIG. 5; and

FIG. 7 is a fragmentary cross-section of a transmission incorporatinghydraulic units with cylinder blocks of the present invention.

While an illustrative embodiment of the invention is shown in thedrawings and will be described in detail herein, the invention issusceptible of embodiment in many different forms and it should beunderstood that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the invention to the embodiment illustrated. The scope of theinvention will be pointed out in the appended claims.

Referring to FIGS. 1, 2 and 3, a generally cylindrical cylinder blockdesignated by the numeral 10 has a central bore 11 therein reduced atone end and internally splined as at 12 to receive and engage a splineddrive shaft. As illustrated, nine cylinder bores 14 are formed in thecylinder block 10 in annular array with their axes parallel to thecenter line of bore 11. The cylinder bores 14 communicate with an endsurface 16 of the cylinder block through axially extending ports 17shown in FIG. 1. Formed radially inwardly of bores 14 are closed endbores 19 in annular array about the center line of bore 11 as shown moreclearly in FIG. 3. The bores 19 are adapted to receive compressionsprings which serve to urge the cylinder block 10 against a stationaryvalve member having arcuate ports adjacent the end surface 16 of thecylinder block 10. Also in annular array about the center line of bore11 are bores 21 which communicate with ports 22 opening to the endsurface 16 of the cylinder block 10. The passages 21 serve to permit theescape of leakage fluid from between the cylinder block and the valvemember (not shown) and discharge of the fluid in the direction of arrow24 in FIG. 1.

The cylinder block 10, as described above, is of the type employed in anaxial piston hydraulic motor, in which pistons reciprocate in cylinderbores 14 as fluid enters and leaves the cylinders through the right endof the cylinder block as viewed in FIG. 1. conventionally, the pistons(not shown in FIGS. 1 to 3) extend from the left end of bores 14 andengage an inclined cam memher or swashplate normally stationary withrespect to the cylinder block and serving to reciprocate the pistons inthe cylinder bores 14. -If the hydraulic unit is acting as a pump, aninput engages the splines 12 in the bore 11 and rotates the cylinderblock against a valve member having two arcuate ports which seriallycommunicate with the bores 14. As the cylinder block rotates, thepistons follow the swashplate or cam member on intake strokes as thecylinder bores pass over one of the arcuate ports in the stationaryvalve member and the cam pushes the pistons into the cylinders ondischarge strokes as the cylinders pass over the other port to deliverfluid under pressure through the other port in the stationary valvemember. When the hydraulic unit is acting as a motor rather than a pump,fluid under pressure admitted to the cylinders pus-hes the pistons whichslide *on the cam and cause rotation of the shaft splined to the block.

The cylinder block 10 is constructed of a high strength steel such as acarbon tool steel, a bearing steel, an air hardening steel or a lowalloy steel. Cylinder sleeves 30 are bonded within each of the cylinderboves 14 to improve the sliding contact characteristics of the pistonsand the cylinder block 10 by a method described in detail below. Thecylinder sleeves 30 may be constructed of an alloy of the base metalssuch as one of the bronzes, AMS 4842, for example. A bearing plate 33 isbonded to end surface 16 of the cylinder block 10 and serves as abearing surface between the cylinder block 10 and the stationary valvemember. Viewing FIG. 2, the bearing plate 33 is annular in shape and hasa central bore 34 concetric with through bore 11 in the cylinder block,and nine annularly arrayed arcuate ports 35 aligned with the axial ports17 in the cylinder block 10. Annularly arrayed ports 36 communicate withpassages 21 and 22 in the cylinder block to discharge leakage fluidescaping between the surface 40, FIG. 1, of the bearing plate and thevalve member (not shown in FIG. 3) in the operation of the hydraulicunit. The bearing plate 33 is constructed of a suitable bearingmaterial, such as bronze, and may be the same material as that employedin the cylinder sleeves 30. It may be seen that the sliding contactbetween the cylinder block 10 and the stationary valve member is on thesurface 40 of the bearing plate and not on the steel portions of thecylinder block so that an improved sliding contact is effected wit-hreduced friction and improved sealing.

The method of bonding the bearing plate 33 and the cylinder sleeves 30to the cylinder block 10 will be described with a specific reference toseveral dissimilar metals, it should be understood that the principlesare applicable to other metals having similar characteristics. It isnecessary that the surfaces to be joined be smooth and have the propersurface finish. For this purpose, the outer diameter of the bushingsmust be finished with the discontinuities and irregularities removedpreferably to a roughness on the order of 16 R.M.S. and the bushing maybe sized in the range of .0003 inch loose fit or clearance in thecylinder b-ore to a .0010 inch interference fit in the bore in order tosecure intimate contact between the outer diameter of the bushing andsurface of the cylindrical bore 14 in the cylinder block. The valveplate 33 should be machined with both faces thereof parallel Within .005inch with bonding surface 45 flat within .0002 inch with discontinuitiesand irregularities removed to a roughness on the order of 10 R.M.S. Thecylinder block 10 is machined so that the cylinder bores 14 have asmooth surface finish with a roughness on the order of 32 R.M.S. and:the end surface 16 is flat and straight within .0002 inch with asurface roughness on the order of 4 R.M.S.

A clamp 50 is employed in the process to secure intimate contact betweenthe bearing plate 33 and the cylinder block 10 during bonding. The clamp50 consists of a first plate 51 having a clamping surface 52 engagingthe rear end of the block through asbestos sheet 54, and a secondclamping member 56 having a clamping surface 57 engaging the bearingplate surface 40 through asbestos sheet 58. The clamping members 51 and56 are urged together by bolt 60 and nut 61. Suitable vents (not shown)are provided in the clamping members 51 and 56 and the asbestos sheetsto permit gas to escape from the cylinders 14 and the bore 11 duringbonding.

In preparing the parts for the bonding operation, it should beunderstood that the bores 14 and 21 in the cylinder block are left blindprior to the bonding operation, and subsequent to bonding the ports 17and 22 in the end of the cylinder block and the registering ports in thebearing plate are suitably machined, as well as any grooving in thesurface 40 of the bearing member. It should also be understood that ifdesired, the bearing plate may initially have an outer diameter greaterthan the diameter of the cylinder block and be suitably machined down tothe diameter of the cylinder block after bonding.

After the bonding surfaces are suitably smooth, the surface oxides areremoved from the cylinder bores 14, the outer surface of the sleeves 30,the end surface 16 of the cylinder block and the bonding surface 45 ofthe bearing plate 33 by any suitable method such as hand scrubbing witha suitable abrasive cleaning agent (such as household cleanser) orcleaning solution. The cylinder block 10, bushings 30 and valve plate 33are then sonic cleaned to remove all foreign matter. These members arethen placed in an acetone bath to assure that the parts are clean untilthe heating process. The clamping fixture 56 should also be cleaned inaccordance with the above cleaning operation.

The bushings 30 are then pressed into the cylinder 14 by a suitablepress. The resulting assembly is then returned to an acetone bathpreparatory to the next operation. The bearing plate is then placed onasbestos sheet 58 on the second clamping member 56 and thereafter thecylinder block is stacked on bonding surface 45 of the bearing plate 33.After the clamping member 51 and the asbestor sheet 54 are placed on theleft end of the cylinder block, bolt 60 is threaded through nut 61 toclamp the parts together as a unitary assembly.

The pressure between the bearing plate 33 and the cylinder block isinitially on the order of 2,000 p.s.i., Within a range of 200 psi. forexample, when clamped in the bonding fixture at room temperature, and isdependent upon the torque applied to nut 61. The criterion is a goodintimate contact between the surfaces to be bonded. Such initialpressure reduces as a function of time in the bonding temperaturethrough loss of strength and creep under load of the steel boltingelement which ties the pieces together. By the end of the bonding cycle,the pressure at the interface may be zero or very close to it.

The pressure at the interface of the bushing and bore is a function ofthe fit of the bushing in the bore initially, the modulus of elasticityof the block and the bushing material, and the diameter, and may varydepending upon the tightness of the fit in the range referred to above.The criterion is a good, snug fit with the pressures ranging from zeroto the yield strength of the bushing which may be on the order of 18,000p.s.i. Of significance is the higher coefiicient of expansion of thebearing inserts which assures a greater expansion of the inserts inorder to maintain pressure between the bearing insert and the wall ofthe cylinder bore during bonding.

While three bonding cycles are described below in detail, with differentbronze bearing metals and steel cylinder blocks, it should be noted thatthe principles of the bonding operation are applicable to the joining ofother dissimilar metals having similar characteristics. However, thespecific steels and bronzes have been found to produce a preferablebond. The bonding cycle is effected by raising the temperature of thebearing met-a1, i.e., in the sleeves and the valve plate 33, to atemperature just within the melting range of the bearing metal so that aportion of the bearing metal is in the liquid phase. This temperaturecorresponds to the austenitizing temperature range of the cylinderblock, which of course is still a solid phase. No fiuxing material orbonding agent or other intermediate materials are employed in thebonding cycle. The bonding temperatures and times are adjusted anddetermined so that bonding proceeds just within the melting range of thebearing metal by maintaining a compatible temperature for austenitizingthe cylinder block and perhaps subsequent direct hardening so thatoverheating or coarsening thereof is avoided. By producing a partialliquid phase of the bearing metal, diffusion of the bearing metaladjacent the interface occurs.

In the first exemplary method, the cylinder block is AISI E52l00 and thecylinder sleeves 30 and the bearing plate 33 are sand, centrifugal, orinvestment cast AMS 4842. The completed cylinder block assembly, removedfrom the bag, is placed in a furnace and preheated at 1300 i25 F. for aminimum of one-half hour. Then the assembly is heated at 1575 F. forapproximately two to two and one-half hours for cylinder blocks underthree and one-half inches in diameter and three to three and one-halfhours for cylinder blocks over three and one-half inches in diameter. Anendothermic atmosphere controlled to a carbon potential neutral to thebase steel is maintained in the furnace during the heating and coolingsteps. An exemplary dew point is between 30 and 35 for the atmosphere.Cooling is then begun by reducing the assembly temperature to 1300 :15F. for two to two and one-half hours. Cooling is continued to room temperature while maintaining a protective atmosphere as by transferringthe assembly to a zone over an oil quench tank heated to 300-350 F. forexample where it is atmosphere cooled for a minimum of thirty minutes.Thereafter, the layup may be removed from the furnace and coolingcontinued at room temperature. The steel cylinder block then has aRockwell C hardness between ten and twenty-five.

The furnace atmosphere is import-ant in that no flux or other thirdmaterial is used in the bonding operation so that clean surfaces andnonoxidizing conditions must be maintained. Best results are obtainedwhen a dry, inert atmosphere is used. Because of availability, astandard endothermic furnace has been generally used and has worked wellenough for production purposes. The endothermic gas atmosphere in suchfurnaces is reducing in nature and is maintained with a carbon potentialneutral to the ferrous member of the assembly being bonded. The pressureneed only be slightly above atmospheric in order to insure againstleakage into the furnace.

A second exemplary bonding cycle is employed for AISI A6 steel cylinderblocks and cast AMS 4842 bearing plates and cylinder sleeves. Afterremoval from the bag, the cylinder block assembly is preheated at 1300:25" F. for a minimum of one hour. Then the assembly is heated at 1575:15" F. for approximately two to two and onehalf hours or three to threeand one-half hours depending upon the block sizes noted above. A similaratmosphere as employed in the first method described above is provided.This completes the bonding and the assembly is then rapidly cooled toproduce transformation and a hardened structure. Tempering of the blockmay then proceed at 500 :10 F. for two to two and one-half hours with aresulting block hardness of between 50 and 60 Rockwell C. The furnacemay be similar to that referred to above.

A third method employs AISI B52100 for the cylinder block the same asthe first method noted above, with cast AMS 4842 bronze cylinder sleevesand bearing plates. Initially, in a vacuum furnace the completedcylinder block assembly is degassed to less than three microns ofmercury at 600 -10 F. The bonding furnace is then back filled with dryargon to produce a non-oxidizing atmosphere at a pressure only slightlyabove atmosphere. Any inert gas may be used such as neon, nitrogen andhelium. The pressure should be above the vapor pressure of the mostvolatile constituent such as the lead in the leaded bronze. Then thecylinder block assembly is preheated at 1300 1 25 F. for at leastone-half hour. The assembly is then heated to 1600 1- 15 F. for two totwo and one-half hours or three to three and one-half hours dependingupon the size of the cylinder block as noted above, and then cooled to1300 125 F. for about two to two and one-half hours. Cooling iscontinued by stepping the temperature of the assembly from 1300" F. to1000 F. in 100 hourly increments for four hours. Thereafter, theassembly is cooled at room temperature after which it is removed fromthe argon atmosphere of the furnace.

Other steels for the cylinder block have been tested satisfactorilyusing the above methods. These steels include A181 4340 and A181 4140.

The specific examples of the methods above are adapted to the type ofsteel and bearing metal employed and the bonding temperature ranges arecontrolled by the physical properties of the bearing material in thesleeves and plate and the steel in the cylinder block. To accomplish thebroad aspects of the present method, the dissimilar metals must bepaired so that a partial, but not complete, melting of the bearing alloyis accomplished while providing an acceptable austenitizing temperaturerange for the steel cylinder block. Somewhat lower temperatures may beemployed if it is not desired that the steel in the cylinder block behardened or if it is to be later hardened by another method, such as theinduction hardening of specific areas of the block.

Referring now to FIG. 4 wherein a photomicrograph of the resulting bondis shown under a 500x magnification. The metal below interface 60 isprimarily the bronze in the bearing plate or cylinder sleeves and themetal above the interface 60 is primarily the steel in the cylinderblock. The photomicrograph is of the interface between an AISI 52100steel cylinder block and an AMS 4842 bronze bearing plate or cylinderbushing, but it should be understood that similar photomicrographs willresult from the use of the other similar metals noted above. It may beseen that a portion of the bronze is diffused above the interface 60 asshown by the light area 61. During bonding, the bronze including thatadjacent the interface 60 partially liquifies, whereby the bronze isthen metallurgically in an alpha plus liquid state, while the steel isin an austenitic state, and the liquified copper in the bronze crossesthe interface 60 and flows into the steel crystalline structure taking asubstitutional position in the iron lattice, producing an intimatemetallurgical bond. Some of the iron may diffuse into the bronze butthis is not illustrated. The bond line shown in FIG. 4 is continuous andcontains no foreign material.

Referring to FIGS. 5 and 6, the diffusion of portions of the metalsacross the interface as determined by an electron microprobe analysis isillustrated in graphic form. FIG. 5 represents a bonding time of onehour and twenty minutes at 1575 F. while FIG. 6 represents the resultingdiffusion after three hours of bonding time at 1575 F. both employingAMS 4842 bronze and 52100 AISI steel. In FIG. 5, it can be seen that fora one hour and twenty minute bonding cycle, the copper in the bronze hasdiffused across the interface between the metals into the steel to adepth of thirty microns from the interface. In FIG. 6, when the threehour bonding cycle is employed, the liquified copper is diffused as faras 60 microns, or even further, from the metal interface into the steel.

Illustrated in FIG. 7 is a hydraulic transmission with axial pistonhydraulic units incorporating the bonded bearing plates 33 and bondedcylinder sleeves 30 on the cylinder block 10 as described with referenceto FIGURES 1 to 3. Like reference numerals in FIG. 7 designate theidentical parts shown in FIGS. 1 to 3. The hydraulic transmissiongenerally indicated by the numeral 80 consists of an axial piston pump81 in back-to-back coaxial relation with an axial piston motor 82. Asthe pump and motor are similar, the components thereof Will be describedwith reference to the pump 81. A gear 86 driven by a suitable primemover is fixed to and drives an input shaft 87 rotatably mounted inbearings 89 and 90. The input shaft 87 is splined at 92 to drive therotating cylinder block 10. A stationary cam member 95 has an inclinedsurface 96 which reciprocates the pistons 98 within the bondedcylindrical sleeves 30. The pistons 98 are connected to the cam memberthrough the ball and socket connections 99.

As the input shaft rotates, driving the cylinders and pistons inrotation, the cam member 95 reciprocates the pistons 98 and fluid isadmitted during piston intake strokes through ports 17 in the steelportion of the cylinder block and ports 35 in the bonded bearing platefrom an arcuate inlet port in a valve member 102 which supports both thepump 81 and the motor 82. During piston discharge strokes, high pressurefluid passes through an outlet port in the valve member 102 and drivesthe pistons in the motor 82 which effects rotation of the cylinder blockof the motor 82 and thereby the output shaft 104 and output gear 105.Hydraulic fluid returning from the motor 82 passes through the arcuateinlet port in the valve member 102 diametrically opposite the outletport and returns to the cylinders in the pump motor block 10 as thepistons move to the right in FIG. 7. Springs seated in bore 19 urge thepistons toward the cam member and a spring 111 urges the cylinder blockand the bearing plate 33 against the valve member 102.

We claim:

1. A reciprocating piston hydraulic unit, comprising, a stationary valvemember having inlet and outlet ports therein, a steel cylinder blockrotatably mounted and having one end thereof adjacent said valve member,said cylinder block having cylindrical bores therein, bronze sleevesbonded within said bores, said cylinder block having a bronze bearingplate bonded on said one end thereof and slidably engaging said valveplate, said bonds consisting of a portion of the bronze substitutionallydiffused in the steel cylinder block, ports in said plate communicatingwith said cylindrical bores, pistons slidably mounted in said sleeves,and an inclined cam member for reciproeating said pistons on rotation ofthe cylinder block.

2. A method of bonding bronze bearing sleeves to a low alloy carbonsteel cylinder block having plural cylinders therein comprising thesteps of; smoothing the surfaces to be joined, cleaning the surfaces tobe joined, press fitting the bronze sleeves into the cylinders, andheating the block between 1550 and 1650 degrees Fahrenheit for a timesuflicient to cause substitutional diffusion of the copper in the bronzeinto the carbon steel.

3. A method of bonding bronze bearing sleeves to a low alloy carbonsteel cylinder block having plural cylinders therein as defined in claim2, wherein the time is sufficient to cause approximately a 20 microndiffusion of the copper into the steel.

4. A method of bonding bronze bearing sleeves to a carbon steelhydraulic unit cylinder block having plural cylinders therein,comprising the steps of; smoothing the surfaces to be joined, cleaningthe surfaces to be joined, press fitting the bronze sleeves into thecylinders, preheating the metals between 1250 and 1350 degreesFahrenheit in a nonoxidizing atmosphere, heating the metals between 1550and 1650 degrees Fahrenheit for at least one and one-half hours, coolingthe metals at approximately 1300 degrees Fahrenheit for at least one andonehalf hours, and then further cooling the metals whereby the copper inthe bronze substitutionally diffuses across the interface into thecarbon steel and forms an intimate metallurgical bond.

5. A method of bonding a bronze bearing plate to a carbon steel pluralcylinder block of a reciprocating piston hydraulic unit having arelatively stationary valve member against which the cylinder blockrotates, comprising the steps of; clamping the bearing plate to the endof the cylinder block to be adjacent the valve member; and heating theplate and the block while clamped to the austenitizing range of thecarbon steel and just within the melting range of the bronze for asufiicient time for the copper in the bronze to substitutionally diffuseacross the interface into the steel and form a metallurgical bond.

6. A method of bonding a bronze valve plate to the working end of -acarbon steel plural cylinder block in a reciprocating piston hydraulicunit having a relatively stationary valve member against which the blockrotates, comprising the steps of; smoothing the surfaces of the blockand the plate to be joined, cleaning the surfaces to be joined, clampingthe bearing plate to the cylinder block, preheating the block and platewhile clamped in a nonoxydizing atmosphere between 1250 and 1350 degreesFahrenheit, heating the block and the plate between 1550 and 1650degrees Fahrenheit for at least one and one-half hours tosubstitutionally diffuse the bronze in the steel, and cooling the blockand the plate at approximately 1300 degrees Fahrenheit.

7. A method of bonding bronze bearing sleeves and a bronze bearing plateto a carbon steel plural cylinder block of a reciprocating pistonhydraulic unit having a relatively stationary valve member against whichthe cylinder block rotates, comprising the steps of; smoothing thesurfaces to be joined, cleaning the surfaces to be joined, press fittingthe sleeves into the cylinder block, clamping the bearing plate againstone end of the cylinder block under a pressure of approximately 2,000pounds per square inch, heating the cylinder block with the sleeves andplate in intimate contact therewith to the austenitizing range of thecylinder block and just within the melting range of the valve plate, andmaintaining that temperature until the copper in the bronzesubstitutionally diffuses across the interface into the carbon steelcylinder block thereby forming an intimate metallurgical bond.

8. A cylinder block for a reciprocating piston hydraulic unit,comprising; a block member constructed of carbon steel and having aplurality of cylindrical bores therein adapted to receive thereciprocating pistons, sleeves constructed of a base metal alloy bondedwithin said bores, said bond consisting of a metallurgicalsubstitutional diffusion of a portion of the base metal in the steelblock.

9. A cylinder block as defined in claim 8, wherein the diffusion of thebase metal extends in the steel from the interface approximately thirtymicrons.

10. A cylinder block as defined in claim 8, wherein the base metal isbronze, and the diffused portion of the said base metal is copper.

11. A cylinder block for a reciprocating piston hydraulic unit,comprising; a carbon steel block member having cylindrical bores thereinopening to a substantially fiat valving surface, and a base metalbearing plate metallurgically bonded to said bock surface, said bondconsisting of a portion of said base metal being substitutionallydiffused across the interface in the carbon steel cylinder block.

12. A cylinder block for a reciprocating piston hydraulic unit,comprising; a steel block member having cylindrical bores therein, andsaid block member having a valve surface on one end thereofcommunicating with said bores, a bronze bearing plate bonded on saidvalve surface, said bond consisting of a portion of the copper in thebearing plate substitutionally diffused across the interface in thesteel block member.

13. A cylinder block as defined in claim 12 wherein said copper isdiffused on the order of 30 microns in the steel.

14. A cylinder block for a reciprocating piston hydraulic unit,comprising; a carbon steel block member having cylindrical borestherein, and said block member having a valve surface on one endthereof; bronze sleeves bonded within said bores, and a bronze bearingplate bonded to said valve surface, said bonds each consisting of aportion of the copper in the bronze being substitutionally diffused inthe steel block across the interface.

15. A cylinder block as defined in claim 14, wherein thesubstitutionally diffused portion of the copper extends from theinterface into the steel a distance in the range of 30-60 microns.

16. A method of bonding base metal bearing sleeves to a carbon steelcylinder block having plural cylinders therein, comprising the step of:smoothing the surfaces of the sleeves and the cylinders to be joined,pressfitting the sleeves into the cylinders heating the metals to theaustenitic temperature range of the carbon steel cylinder block and justwithin the melting range of the base metal sleeves whereby the basemetal is in a partial liquid state, and maintaining that temperature fora time sufiicient to cause substitutional diffusion of a portion of theliqui fied base metal across the interface into the carbon steel.

17. A method of bonding a flat base metal bearing plate to a carbonsteel plural cylinder block of a reciprocating hydraulic unit having astationary valving member against which the cylinder block rotates,comprising the steps of: clamping the base metal bearing plate to theend of the cylinder block to be adjacent the stationary valving member,and heating the plate and the block while clamped until a substitutiondiffusion of the base metal across the interface in the steel produces ametallurgical bond.

References Cited by the Examiner UNITED STATES PATENTS 2,190,237 2/ 1940Koehring 29-420 2,226,944 12/1940 Reeve 29-498 2,307,041 1/1943 Hawleyet al. 103-162 2,373,117 4/1945 Hobrock 29-498 2,633,628 4/1953 Bartlett29-420 2,850,798 9/1958 Bowman et al. 29-498 2,856,281 10/1958 Cremer etal. 29-504 2,998,646 9/ 1961 Hitz 29504 3,142,262 7/1964 Firth et al103-162 3,191,543 6/1965 Hann et al. 103-162 MARTIN P. SCHWADRON,Primary Examiner.

EDGAR W. GEOGHEGAN, Examiner.

R. M. VARGO, Assistant Examiner.

Disclaimer 3,2S),758.W2Tls0n Leeming, James E. Knabe, and Richard 0.Bm'zfton, Rockford, I11. CYLINDER BLOCK OF A HYDRAULIC UNIT AND METHODOF MAKING SAME. Patent; dated Oct. 25, 1966. Disclaimer filed Feb. 25,1977, by the assignee, Sunclstmwd Corpamtz'on. Hereby enters thisdisclaimer to claims 1, 5, 8, 10 to 12, 14 and 17 of said patent.

[Ofiica'al Gazette April 19, 1.977.]

1. A RECIPROCATING PISTON HYDRAULIC UNIT, COMPRISING, A STATIONARY VALVEMEMBER HAVING INLET AND OUTLET PORTS THEREIN, A STEEL CYLINDER BLOCKROTATABLY MOUNTED AND HAVING ONE END THEREOF ADJACENT SAID VALVE MEMBER,SAID CYLINDER BLOCK HAVING CYLINDRICAL BORES THEREIN, BRONZE SLEEVESBONDED WITHIN SAID BORES, SAID CYLINDER BLOCK HAVING A BRONZE BEARINGPLATE BONDED ON SAID ONE END THEREOF AND SLIDABLY ENGAGING SAID VALVEPLATE, SAID BONDS CONSISTING OF A PORTION OF THE BRONZE SUBSTITUTIONALLYDIFFUSED IN THE STEEL CYLINDER BLOCK, PORTS IN SAID PLATE COMMUNICATINGWITH SAID CYLINDRICAL BORES, PISTONS SLIDABLY MOUNTED IN SAID SLEEVES,AND AN INCLINED CAM MEMBER FOR RECIPROCCATING SAID PISTONS ON ROTATIONOF THE CYLINDER BLOCK.